The present invention relates generally to techniques for determining the oxidative status of dry or intermediate moisture foods and more particularly to a novel technique for determining the oxidative status of packaged dry or intermediate moisture foods.
Lipids present in dry or intermediate moisture foods are susceptible to becoming rancid as a result of oxidation. This rancidity caused by oxidation is a major cause of food deterioration. The acceptability of a food product often depends on the extent to which such deterioration has occurred. Therefore, some technique for assessing the extent of oxidation arid for predicting remaining storage life is necessary. Sensory analysis is one of the most sensitive methods available. However, this method is obviously not practical for routine analysis. As a result, many chemical and physical techniques have been devised in an effort to quantify oxidative deterioration and to correlate the data with off-flavor development. Chemical methods include those which measure peroxide value, the thiobarbituric acid test, the Kreis test, those which measure total and volatile carbonyl compounds, and oxirane determination tests. Physical methods include ultraviolet and infrared spectroscopy, polarography, gas chromatography and refractometry. All of these methods, however, employ high temperature, or strong acid or solution, which classify such methods as destructive methods.
In U.S. Pat. No. 4,253,848 to Porter, which issued on Mar. 3, 1981 and which is incorporated herein by reference, there is disclosed a rapid, dry, room temperature, non-destructive method for assaying the oxidative status of unsaturated lipids in whole foods, fats or oils. Said method involves exposing dissolved or volatile compounds from oxidizing lipids to a plastic or glass strip coated on one side with a polyamide (poly-.epsilon.-caprolactam) coating and then observing a bluish-white fluorescence from the polyamide coating upon illumination with ultraviolet light. In accordance with the method disclosed in the aforementioned patent, illumination of the polyamide coating takes place from the direction of the exposed side of the polyamide coating, and observation of the resultant fluorescence typically takes place from the same side. Although some mention is made in the patent to applying the method disclosed therein to the inspection of packaged goods, the patent does not provide information as to how said inspection could be effected in an accurate and reproducible way and without requiring the opening of the package containing the goods.